A few possibilities come to mind. The first is that even though you had a conversation about a topic, don’t assume that he was fully paying attention. Relatedly, many people are guilty of being distracted by their electronic devices and thus are only half paying attention. If so, his divided attention could explain it.
Perhaps these experiences are evidence of a degrading memory or another cognitive problem. You didn’t mention the condition of his health so memory issues may or may not be applicable.
Try to focus on what is happening during your conversations and note if any of the aforementioned possibilities could explain the problem. If his health is a concern, he should be evaluated by a physician.
If I were interviewing you in person, I’d want to know if you’ve asked him about this issue. “Why did you start dinner when we just agreed to order pizza?” Does he deny your earlier conversation? Does he remember once he is reminded? You might gain insight into this issue by asking him directly.
Thank you for your question. Please take care.
Dr. Kristina Randle